The correct answer is D. Phosphorous.
Phosphorus is a chemical element with the symbol P and atomic number 15. It is a non-metallic, pale yellow, odorless, tasteless, and highly flammable element. Phosphorus is the most reactive of all the non-metals, and is classified as a metalloid. It is found in nature in the form of phosphate rocks, and is used in a variety of applications, including fertilizers, pesticides, and semiconductors.
In CRTs, phosphorus is used to coat the inside of the face of the tube. When an electron beam strikes the phosphorus, it causes the phosphorus to emit light. The color of the light emitted depends on the type of phosphorus used. For example, red phosphorus emits red light, green phosphorus emits green light, and blue phosphorus emits blue light.
The other options are incorrect. Carbon is a non-metallic element with the symbol C and atomic number 6. It is a solid at room temperature and is found in nature in the form of coal, diamonds, and graphite. Carbon is the basis of all organic compounds, and is used in a variety of applications, including plastics, fuels, and semiconductors.
Sulphur is a non-metallic element with the symbol S and atomic number 16. It is a yellow, odorless, and tasteless element that is found in nature in the form of sulfur crystals. Sulphur is used in a variety of applications, including fertilizers, pesticides, and rubber.
Silicon is a metalloid with the symbol Si and atomic number 14. It is a hard, brittle, and non-metallic element that is found in nature in the form of sand. Silicon is used in a variety of applications, including semiconductors, solar cells, and glass.